Between 2005 and 2011 he had management roles at League of Ireland club Galway United. He is also active on the keynote and after-dinner speaking circuit, where he advises companies about risk and corporate responsibility.
He also competed in Celebrity Big Brother 2018, where he finished in 4th place.

In 1992, he was appointed general manager of a new operation in futures markets on the Singapore International Monetary Exchange (SIMEX).[3] Barings had held a seat on SIMEX for some time, but did not activate it until Leeson was sent over. Leeson was sent to Singapore after he was denied a broker's licence in the United Kingdom because of fraud on his application.[4] Neither Leeson nor Barings disclosed this denial when Leeson applied for his licence in Singapore.[5]

From 1992, Leeson made unauthorised speculative trades that at first made large profits for Barings: £10 million, which accounted for 10% of Barings' annual profit.[6] He earned a bonus of £130,000 on his salary of £50,000 for that year.

However, Leeson's luck soon went sour and he used one of Barings' error accounts (accounts used to correct mistakes made in trading) to hide his losses. The account was numbered 88888.[7][8] Leeson claims that this account was first used to hide an error made by one of his colleagues; rather than buy 20 contracts as the customer had ordered, she had sold them, costing Barings £20,000.[9][10]

However, Leeson used this account to cover further bad trades. He insists that he never used the account for his own gain, but in 1996 The New York Times quoted "British press reports" as claiming that investigators had located approximately $35 million in various bank accounts tied to him.[3]

Management at Barings Bank also allowed Leeson to remain chief trader while also being responsible for settling his trades, jobs usually done by two different people. This made it much simpler for him to hide his losses from his superiors.[11]

By the end of 1992, the account's losses exceeded £2 million, which ballooned to £208 million by the end of 1994.

The beginning of the end occurred on 16 January 1995, when Leeson placed a short straddle in the Singapore and Tokyo stock exchanges, essentially betting that the Japanese stock market would not move significantly overnight. However, the Kobe earthquake hit early in the morning on 17 January, sending Asian markets, and Leeson's trading positions, into a tailspin. Leeson attempted to recoup his losses by making a series of increasingly risky new trades (using a long-long future arbitrage), this time betting that the Nikkei Stock Average would make a rapid recovery. However, the recovery failed to materialise.

Leeson left a note reading "I'm Sorry" and fled Singapore on 23 February. Losses eventually reached £827 million (US$1.4 billion), twice the bank's available trading capital. After a failed bailout attempt, Barings, which had been the United Kingdom's oldest merchant bank, was declared insolvent on 26 February.[12]

After fleeing to Malaysia, Thailand, and finally Germany, Leeson was arrested in Frankfurt and extradited back to Singapore on 20 November 1995, though his wife Lisa was allowed to return to England. While he had authorisation for the 16 January short straddle, he was charged with fraud for deceiving his superiors about the riskiness of his activities and the scale of his losses. Several observers have placed much of the blame on the bank's own deficient internal auditing and risk management practices. Indeed, the Singapore authorities' report on the collapse was scathingly critical of Barings management, claiming that senior officials knew or should have known about the "five eights" account.

Leeson pleaded guilty to two counts of "deceiving the bank's auditors and of cheating the Singapore exchange",[2] including forging documents.[13] Sentenced to six and a half years in Changi Prison in Singapore, he was released from prison in 1999, having been diagnosed with colon cancer, which he survived despite grim forecasts at the time.

While in prison, in 1996, Leeson published an autobiography, Rogue Trader, detailing his acts. A review in the financial columns of the New York Times stated, "This is a dreary book, written by a young man very taken with himself, but it ought to be read by banking managers and auditors everywhere."[3] In 1999, the book was made into a film of the same name starring Ewan McGregor and Anna Friel.

Leeson's first wife Lisa divorced him while he was in prison. He married Leona Tormay in 2003,[15] and they now live in Barna, County Galway, in the west of Ireland. He is a regular guest on the after-dinner and keynote speaking circuit[16][17] and occasional guest lecturer at the nearby National University of Ireland. He was appointed commercial manager of Galway United F.C. in April 2005, rising to the position of general manager in late November 2005. By July 2007 he had become the club's CEO[18] but in February 2011, Leeson resigned his position.[19] He still deals in the stock markets, but only with his own money.[18]

In June 2005, Leeson released a new book, Back from the Brink: Coping with Stress. It picks up his story where Rogue Trader left off, including in-depth conversations with psychologist Ivan Tyrrell asserting that the prolonged periods of severe stress that affected Leeson's mental and physical health[context?] have parallels in many other people's lives.

On 5 April 2007, The Guardian newspaper reported that KPMG, the liquidators of Barings PLC, had sold a trading jacket thought to have been worn by Nick Leeson while trading on SIMEX in Singapore. The jacket was offered for sale on eBay but it failed to reach its reserve price despite a highest bid of £16,100. It was subsequently sold for £21,000.[22] In October 2007 a similar jacket used by Leeson's team but not thought to have been worn by Leeson himself sold at auction for £4,000.[23]